This invention relates to a high pressure condensate return unit for use in high pressure condensate return systems in steam systems. More particularly, this invention relates to such an apparatus for returning condensate from high pressure steam systems directly to a boiler in a way in which the release of vapors is eliminated and without a throttling of the pump suction or discharge while maintaining adequate provision for deaeration without external condensate flow rate controls. Still more particularly, this invention relates to such a unit as described, a system for utilizing such a unit to return high pressure condensate directly to the boiler at a rate consistent with the condensate input to the apparatus, and to a method for using the same in a steam generating system.
It is an overall purpose of the invention disclosed and described herein to save energy. In steam generating systems of the prior art which involve the use of steam, wherein the steam is condensed at high pressure and temperature, the condensate from the process vessels is returned to the steam generating system. In the prior art, the predominantly known method for returning this condensate is through the use of mechanical steam traps to separate the condensate from the steam in the vessel, and utilizing steam pressure to force the condensate back to an atmospheric or lower pressure receiver. The receiver in such systems acts as a collection point, surge tank, feedwater make-up tank, and point of removal for air and other non-condensible gases from the condensate. The feedwater is thereafter pumped from the receiver back to the boiler using high pressure pumps which are automatically controlled.
It is a continuing problem in the use of such systems in that when the condensate is returned from the process to the receiver, a large amount of vapor is flashed through the receiver vent pipe as the condensate is cooled from the saturated steam temperature to its saturation temperature at the receiver pressure. Quite often, the condensate is cooled to 212.degree. F. because the receiver is often at atmospheric pressure or in communication with the atmosphere. In order to maintain a relatively constant volume of feedwater in the system, the make-up water at ambient temperature, such as 60.degree. F., is periodically added to the system to replace the volume of steam flashed to the atmosphere. This water plus the remaining condensate must therefore be reheated to the saturation temperature inside the boiler before steam can be regenerated. This results in significant energy losses resulting from the energy wasted due to the flashing of the condensate to the steam. In addition, losses are incurred in pumping costs since the condensate must be raised from a zero or low pressure back to the boiler pressure by the feedwater pumps.
Also in the prior art, such losses have been sought to be minimized or eliminated by the development of high pressure condensate return systems. However, with such systems there has typically been a need to depress the temperature or pressure of the condensate in order to pump the condensate or to throttle the pump discharge for the control causing undue wear of seals, impellers, and bearings of the requirement to cycle the pump. Such units have had only limited provisions for the removal of air and non-condensible gases consisting generally of simple bleed lines for flashing a small amount of condensate from a very low surface area. Moreover, the overall design of such systems has required an elaborate and expensive control system to assure pumping rates.
Thus, it is an overall aspect of this invention to provide a high pressure condensate return unit for high pressure systems designed to return the condensate directly to the boiler while bypassing the feedwater system in a way which eliminates the need to release vapors at any point in the system and without throttling the pump suction or discharge while yet providing adequate provisions for deaeration without the need for elaborate controls.
These and other overall objects of the invention will become apparent from a written description of the invention which follows.